A vehicular system controlling lock or unlock of a door of a vehicle has been known. This kind of vehicular system controls a state switch between a lock state and an unlock state of each door of the vehicle according to an ID code comparison result between a mobile device, such as an electronic key, and a vehicle side unit via a wireless communication. This kind of system also permits an engine start under a condition that a person who carries the mobile device is in a compartment of the vehicle.
Technologies for avoiding locking the door with a mobile device left in the vehicle have been proposed for above-described vehicular system. Specifically, when multiple mobile devices are registered to one vehicle, the user may lock the door with one or more registered mobile devices left in the vehicle (for example, refer to patent literature 1).
In order to solve above-described difficulty, patent literature 1 discloses a vehicular system which determines the door lock with the mobile device left in the vehicle. Specifically, the vehicle side unit transmits a request signal to the inside space of the vehicle compartment. When the vehicle side unit receives a response signal from the registered mobile device, the vehicle side unit determines the door lock with the mobile device left in the vehicle.
In patent literature 1, the vehicle side unit transmits, as the request signal, ID code or key number code indicating key number. When a mobile device corresponding to the code transmitted as the request signal exists in the vehicle compartment, the mobile device returns a response signal. When the response signal is transmitted from the mobile device, the vehicle side unit determines the presence of the mobile device, which has the same code with the code transmitted in the request signal, in the vehicle. In patent literature 1, the vehicular system carries out the process (hereinafter, determination process), which determines whether the mobile device is left in the vehicle, for all of the registered mobile devices in order to determine the presence of each mobile device in the vehicle compartment. In the determination process, the request signal is transmitted to the mobile device, and the presence of the mobile device is determined based on whether the response signal is transmitted from the mobile device in response to the request signal.
In the vehicular system disclosed in patent literature 1, it takes quite a long time for determining the presence of all of the registered mobile devices in the vehicle compartment. The following will describe the details.
The mobile device transmits the response signal as a response only when the request signal transmitted from the vehicle side unit designates the mobile device itself. For determining the presence of all of the registered mobile devices in the vehicle compartment, the vehicle side unit needs to perform above-described determination process to each of the registered mobile devices in a predetermined order even in a case where only one mobile device (hereinafter, referred to as registered mobile device) that is registered to the vehicle exists in the vehicle. Thus, the vehicular system disclosed in patent literature 1 always requires quite a long time for determining the presence of all of the registered mobile devices in the vehicle compartment. That is, the vehicular system always requires a certain time period for performing the determination process for all of the registered mobile devices regardless of the actual number of the mobile devices that remain in the vehicle compartment.